[PATCH 2/8] drm/tegra: Allocate BOs from lower 4G when without IOMMU

[Mikko Perttunen]

On 05.12.2016 20:39, Thierry Reding wrote:
> On Thu, Nov 10, 2016 at 08:23:39PM +0200, Mikko Perttunen wrote:
>> On 64-bit Tegras, buffer object memory allocation may
>> return memory above 4G that units behind Host1x cannot
>> access. Add the GFP_DMA flag to these allocation when
>> IOMMU is not enabled to ensure units can always access
>> BO memory.
>
> I don't think that's entirely true. The display controller can address
> more than 32 bits. It's perhaps slightly different from other units that
> are behind host1x, but maybe we need a special case here to allow frame-
> buffers to reside in higher memory?

I checked and looks like all (or at least most) units can actually 
address 34 bits /almost always/. The thing that tripped me up was that 
apparently the firmware for VIC still needs be in the lower 32 bits. So 
we should be able to drop this patch.

>
> Thierry
>

Thanks,
Mikko.